The goal of this proposal is to evaluate two non-invasive techniques for detecting in-stent restenosis and based on the results design a compact clinical device that can be used in a doctor's office. An estimated seven million American suffer from coronary artery disease, which causes 1.5 million myocardial infarctions. Currently, the preferred treatment to open occluded arteries is a combination of angioplasty and stenting. This combination has over the past years significantly reduced the occurrence of restenosis in the treated area. Yet, restenosis rates can still be as high as 25% in high-risk populations. Current techniques for detecting restenosis include coronary angiography, radionuclide ventriculography, and intravascular ultrasound. These techniques are expensive, time consuming, and invasive. Our proposed takes advantage of the fact that the dielectric properties of blood and plaque can differ by as much as an order of magnitude over the frequency range extending from 100 MHz to 10GHz. Consequently, the electromagnetic scattering spectrum of a stent will change as plaque forms. By measuring this change over time we expect to identify potentially dangerous restenosis. This type of device is only now practical because of significant advance in wireless communication technology.